Filming a movie about sexual fantasy isn't always fun and games. At least, it wasn't for Dakota Johnson.

In a new interview with Marie Claire, the Fifty Shades of Grey actress got candid about the most eccentric aspects of filming the BDSM franchise — starting with the scene that Johnson called "the most difficult one by far," which occurs in the final installment, Fifty Shades Freed.

In the scene, Johnson, as Anastasia Grey (née Steele), has her arms and legs handcuffed to a gate while she's blindfolded. "And it was kind of shocking, because I didn't realize that no matter how prepared or rehearsed I was, when your senses are taken away like that, you can't control the way your nervous system will react," she said. "So it was really tricky to navigate that scene. It was kind of difficult."

Also difficult: Getting used to the strapless thongs that had to be superglued to her body once the adhesive wore off. "They're, like, basically if it were a nipple pastie, but underwear," Johnson described, later adding, "It's not painful, I mean, it's barely anything. But I guess you have some sense of being covered. It's fucking bizarre."